1. Field of the Invention
The present invention relates to the field of fuel injectors.
2. Prior Art
Conventional 2-way needle control valves to control the motion of a diesel injector's needle valve have been in use for quite some years. They provide acceptable but not superior controllability with relatively low cost. On the other hand, needle control with 3-way valves has not been commercialized to the same extent. They provide superior flexibility in controlling the needle motion, but with relatively higher cost.
Direct needle control with 2-way valves is relatively simpler and lower cost. However, the flexibility in controlling the needle motion during both opening and closing through the entire pressure range is not optimal.
Previous direct needle control injectors with 3-way valves achieved superior needle controlling flexibility, but they were complex and costly. Also, the orifice determining the needle opening velocity is farther from the needle control volume than ideal.